High Methylene Blue Adsorption Capacity Research Articles

ZIF-8-derived photocatalyst membrane for water decontamination: From static adsorption-degradation to dynamic flow removal

Photocatalysis has been considered a promising method for environmental purification. However, powder nanomaterials are not suitable for large-scale application due to the limit of low recyclability and energy-intensive operation. Integrating and depositing powder photocatalysts on monolithic substrates may solve these issues. In this study, a ZIF-8 photocatalyst membrane and its derived product (ZnS photocatalyst membrane) was constructed by a facile in-situ treatment of cellulose-based substrate (take filter paper as an example). Both the two nanomaterials were confirmed to be tightly anchored to filter paper with the aid of chemical interaction. Under visible light irradiation, excellent dynamic-flow photocatalytic removal efficiencies of methylene blue (MB) degradation (97% within 80 min, k = 0.042 ± 0.002 min−1) and Cr(VI) reduction (100% within 60 min, k = 0.116 ± 0.007 min−1) were achieved by the prepared ZIF-8 photocatalyst membrane and its derived ZnS photocatalyst, respectively. Considering the high MB adsorption capacity and facile regeneration process of ZIF-8 photocatalyst membrane, the adsorption-degradation strategy was promising for its universal applications. The MB degradation pathway and photocatalytic mechanisms were also explored. Ultimately, a comprehensive discussion on the advantages and implications of prepared photocatalyst membranes for photocatalytic water treatment was rationally proposed. This study provided a promising method for water decontamination and demonstrated the significant superiority of monolithic membrane for photocatalytic water treatment.

Adsorptive Removal of Methylene Blue from Aqueous Solutions Using Magnetic Fe3O4@C-dots: Removal and kinetic studies

ABSTRACT The Fe3O4@C-dots produced from Elaeagnus Angustifolia, has been applied as an adsorbent for the removal of methylene blue (MB) from aqueous solutions. The prepared Fe3O4@C-dots exhibited a noticeably higher adsorption capacity for MB, reported to be 124.39 mg/g when compared to the results of many other documented references. Furthermore, after evaluating the effects of various parameters on the adsorption capacity of Fe3O4@C-dots, it was discovered that the adsorption capacity increased with the contact time, pH, and MB initial concentration, respectively. Furthermore, the impacts of pH on adsorption were strongly amplified through pHzpc. According to the results, electrostatic interactions, hydrogen bonding, and chemical binding comprise the adsorption mechanism between the MB molecules and adsorbent. The MB adsorption was identified through the kinetic studies to be dominated through the model of pseudo-second-order kinetic. Also, the isotherm analysis showed that the adsorption process is consistent with the Langmuir equations. As the Fe3O4@C-dots were subjected to recycling, no significant changes were observed throughout the adsorption capacity after five regeneration cycles. Considering how the outcomes indicated the capability of magnetic nanoparticles in performing an effective MB removal, we can recommend the high potential of this adsorbent for the clearance of cationic dyes from wastewater.

Adsorption kinetics of simulated mixture wastewaters over porous Bi2MoO6@BiOCl@MOF-199 heterostructure

In this work, we mainly investigate the adsorption properties of the simulated single and mixture wastewaters over porous Bi2MoO6@BiOCl@MOF-199 (BMO@BOC@MOF-199), including methylene blue (MB), rhodamine blue (RhB), methyl orange (MO) and chromium (VI). It is found that BMO@BOC@MOF-199 has a high adsorption capacity for MB, but a poor adsorption capacity for MO. Specifically, for single MB solution, 67%, 80% and 96% of MB are adsorbed by BMO@BOC, MOF-199 and BMO@BOC@MOF-199, respectively. The higher adsorption capacity of BMO@BOC@MOF-199 could be due to its higher surface area and larger pore volume. For single MO solution, nevertheless, only 16%, 13% and 7% of MO are adsorbed by BMO@BOC, MOF-199 and BMO@BOC@MOF-199, respectively. The different adsorption efficiency for MB and MO could be relative to their different molecular structures, which have different electrostatic interactions with adsorbent surface. For single RhB and single Cr(VI) solution, BMO@BOC@MOF-199 has adsorbed 30% RhB and 10% Cr(VI). In RhB-MO mixture solution, 32% RhB and 9% MO can be adsorbed by BMO@BOC@MOF-199, while in Cr(VI)–RhB-MO mixture solution, 7% Cr(VI), 3% RhB and 42% MO can be adsorbed by BMO@BOC@MOF-199. It is seen that in RhB-MO mixture solution, the adsorption efficiencies of RhB and MO by BMO@BOC@MOF-199 do not obviously change as compared to single RhB and single MO solution, while in Cr(VI)–RhB-MO mixture solution, the adsorption efficiency of MO has increased by 5 times, compared to single MO solution; but the adsorption efficiency of RhB has decreased by 9.7 times as compared to single RhB solution, and the adsorption efficiency of Cr(VI) has decreased slightly, compared to single Cr(VI) solution. The results are mainly attributed to the competitive adsorption on the adsorbent surface. This work can help us to understand the adsorption process for practical wastewater.

Development of Eco-friendly Adsorbent Pellets from Low Fire Clay and Potato Starch for Potential Use in Methylene Blue Removal in Aquaculture

Mesoporous clay-starch ceramic pellets have been prepared using silica-rich low fire clay and potato starch as a pore-forming agent. The ceramic pellets prepared using 30% starch, showed the highest porosity and lowest compressive strength among all the different pellets. Batch mode studies using the pellets showed higher methylene blue adsorption capacity with an increase in time and increased initial dye concentration. The adsorption capacity was found to decrease with increasing pellet dose, while pH had a negligible effect on methylene blue removal which makes them a suitable adsorbent in both acidic and basic mediums. Adsorption isotherm analysis of the process was followed by the Langmuir adsorption isotherm whereas the kinetics analysis fitted well with the pseudo-second-order kinetic model. A low-cost, simple device was made from a stainless-steel wire mesh with mesoporous ceramic pellets enclosed in it, which can easily be dipped and taken out of an aquarium and can remove methylene blue from water.

Calcium alginate‐regenerated spent bleaching earth composite beads for efficient removal of methylene blue

AbstractThis study aims to find an alternative method to the landfill of spent bleaching earth (SBE), which is a solid waste generated by the refining of edible oil that causes enormous ecological and environmental problems. This solid waste is clay loaded with impurities, colourants, and a large amount of oil entrained during the various stages of refining. In this study, the SBE was initially regenerated (RSBE) by thermal processing in a muffle furnace (temperature: 400°C, time: 1 h) followed by washing with an HCl solution. Then, the regenerated materials were encapsulated with calcium alginate (Alg) to form adsorbent composite beads (Alg‐RSBE). Different Alg/RSBE ratios were applied during materials elaboration, yielding beads denoted Alg‐RSBE 1/1 (1/1, w/w), Alg‐RSBE 1/2 (1/2, w/w), and Alg‐RSBE 1/3 (1/3, w/w), respectively. The Alg–RSBE composite beads were characterized by several methods (FTIR, SEM, EDX, TGA, pHPZC) and used as adsorbents of methylene blue (MB) in a fixed‐bed adsorption system. The adsorption of MB was studied at different experimental conditions such as contact time and initial MB concentration. The results showed that the kinetics of MB adsorption fitted to pseudo‐second‐order kinetics and the adsorption isotherm fitted to Langmuir isotherm. Among the three types of Alg‐RSBE composite beads, Alg‐RSBE 1/1 presents the highest MB adsorption capacity at 833.33 mg/g. Intraparticle and film diffusion equations were used to evaluate the kinetic data. Finally, the regeneration study showed that MB dye was successfully desorbed from Alg‐RSBE 1/1 with removal percentages from 93.32% to 88.15% after six cycles.

Study on Adsorption of Nickel and Methylene Blue in Aqueous Solution by Magnetic Carboxylate-Rich Carbon

In this study, magnetic carboxylate-rich carbon material (Fe3O4@CRC) was synthesized via a low-temperature carbonization method and applied as an adsorbent for adsorption of Ni(II) ions and methylene blue (MB) in aqueous solution. The synthesized Fe3O4@CRC was characterized by various techniques (XRD, FTIR, FE-SEM, TEM, EDX, VSM, and BET). The adsorption kinetics, isotherms, thermodynamics, and the effects of key adsorption factors, including the pH value, initial adsorbate concentration, contact time, adsorbent dose and temperature were investigated in detail. The results showed that Fe3O4@CRC exhibited a high adsorption capacity for MB and Ni(II) with the maximum adsorption capacity of 187.26 mg/g and 106.75 mg/g, respectively. The adsorption of MB and Ni(II) on Fe3O4@CRC was a spontaneous and endothermic process, and was best described with the first-order kinetic model, Freundlich (for MB) and Langmuir (for Ni(II)) isotherm models. In addition, Fe3O4@CRC could maintain a high adsorption capacity after many consecutive cycles. Therefore, the Fe3O4@CRC material can be used as a highly efficient adsorbent for the removal of heavy metals and dyes from wastewater due to the advantages of high adsorption performance, easy separation, and good reusability.

Preparation and characterization of an aluminosilicate material with layer expansion structure

The aluminosilicate material with layer expansion structure was prepared by the first urea intercalation and subsequent rapid calcination of kaolinite-urea intercalation complex with urea and potassium chlorate. The driving force for expanding kaolinite layer to obtain the aluminosilicate material was the energy released by the reaction of added urea and KClO3 at high temperature. The mass ratio of urea to KClO3 (U/P ratio) had a positive correlation with the energy released by the reaction. The expansion degree of kaolinite layer could be controlled by adjusting U/P ratio through the control of released energy. When U/P ratio exceeded 0.49, the 001 reflection of kaolinite completely disappeared, indicating the full expansion of aluminosilicate layers. The SEM and TEM images revealed that the layers were expanded to form a fishing net-like porous structure with the layer thickness in the range of about 20 to 190 nm. The specific surface area and the total pore volume of the aluminosilicate material was found to be 2.5 and 2.7 times larger, respectively, than that of the raw kaolin. The aluminosilicate material surface was more negatively-charged with higher absolute ζ-potential and higher methylene blue adsorption capacity than the raw kaolinite. The expansion treatment of layer structure was an efficient and facile method to expand the application field of kaolinite.

Effect of cations on the enhanced adsorption of cationic dye in Fe3O4-loaded biochar and mechanism

Fe3O4-loaded biochar (MBC) was synthesized through oxygen-limited pyrolysis of FeCl3-impregnated sorghum straw biomass, and its performance and mechanism for the adsorption of cationic methylene blue (MB) were investigated. The FeCl3 concentration of the modified solution used for MBC synthesis was optimized, and the physicochemical properties of the prepared adsorbents were evaluated. The results showed that iron oxide particles were successfully introduced on the biochar, resulting in a higher adsorption capacity for MB. The adsorption kinetics of MB onto raw biochar (BC) and MBC were better fitted to the pseudo-second-order model. The Freundlich isotherm model best described the experimental isotherm for MB adsorption onto BC, while the Langmuir model was best for MB on MBC. The presence of cations with different valences (Na+/ Cu2+/Zn2+/Cr3+) induced a positive effect on the adsorption capacities of MBC for MB, which increased from 133.13 mg/g to 166.67, 160.21, 162.95, and 155.72 mg/g, respectively. Importantly, there was synergistic adsorption between MB and Cu2+/Zn2+/Cr3+, and the mechanistic study indicated that the MB molecules and Cu2+/Zn2+/Cr3+ acted as a bridge between the adsorbed and unadsorbed pollutants, which significantly improved the synergistic adsorption between dyes and heavy metal cations.

Fast and mild alkaline solvothermal synthesis of nanostructured flower-like Na2Ti3O7 and its methylene blue adsorption capacity

This work reports a facile solvothermal synthesis of hierarchical flower-like Na2Ti3O7 structures with fast and high methylene blue adsorption capacity. A mesoporous architecture of Na2Ti3O7 with a surface area of 159.63 m2-g-1 was produced under mild alkaline conditions (2 M NaOH) and a short reaction time (8 h). Interestingly, methylene blue adsorption equilibrium on the Na2Ti3O7 powders was achieved in a short time of 10 min. The pseudo-second-order kinetic model and the Langmuir isotherm model described the adsorption mechanism. The synthesized Na2Ti3O7 powders have interesting features that highlight their suitability for environmental applications.

Valorization of spent activated carbon in glycerine deodorization unit for methylene blue removal

Spent Calgon Filtrasorb activated carbon (SAC) from glycerine deodorization unit was evaluated for the removal of methylene blue (MB). The SAC was used without further modification. The SAC was characterized for BET surface area, pH, pHpzc and FTIR to determine the textural and chemical properties of SAC. The batch adsorption study of MB was carried out under different initial concentrations (5–500 mg/L), pH (2–11) and contact time (0–200 h). The SAC was found to have high BET surface area, pore volume and average pore diameter of 735 m2/g, 0.292 cm3/g and 2.56 nm, respectively. The properties of SAC contributed to high MB adsorption capacity of 283 mg/g. The equilibrium data fitted well with Langmuir model, indicating monolayer adsorption; while the activation energy (Ea) of Dubinin–Radushkevitch (D–R) model is lower than 8 kJ/mol, signifying physisorption. The adsorption kinetics was best illustrated by pseudo-second-order model, while the intraparticle diffusion and Boyd models suggested that film diffusion is the rate-controlling step. These findings showed that Calgon Filtrasorb SAC from glycerine deodorization unit can be potentially reused an adsorbent for the removal of dyes.

Facile mechano-chemical synthesis and enhanced photocatalytic performance of Cu2ZnSnS4 nanopowder

In the present study, Cu2ZnSnS4 (CZTS) powder was synthesized by the mechano-chemical method from its elemental constituents. X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and diffusion reflectance spectroscopy (DRS) were used for characterization of structural, morphological and optical properties. XRD result confirmed that a highly crystalline CZTS phase corresponding to the kesterite structure was formed after 50 h ball milling. Raman analysis confirmed the existence of single phase CZTS without any other phases. FESEM and TEM images reveal the irregular CZTS nanoparticles with an average size of 90 nm. The elemental mapping of the CZTS nanopowder showed the uniform distribution in agreement with the stoichiometry. DRS result showed a band gap value of 1.53 eV. XPS result revealed the oxidation states as Cu+, Zn2+, Sn4+ and S2−. The photocatalytic activity of CZTS has been investigated through photodegradation of methylene blue (MB) and methyl orange (MO) dyes solution with different concentrations under visible light irradiation. Although the CZTS decomposed MO only 81% until 210 min, the MB solution was completely photodegraded after 100 min. A kinetic study by Langmuir-Hinshelwood (L-H) model indicated about 3.7 times faster degradation of MB than MO and also higher adsorption capacity for MB by CZTS. Furthermore, the prepared CZTS was reusable and can be repeatedly used for the removal of dyes from aqueous solutions.

Solvent-free synthesis of magnetic biochar and activated carbon through ball-mill extrusion with Fe3O4 nanoparticles for enhancing adsorption of methylene blue

Magnetic carbonaceous adsorbents were synthesized by ball-milling biochar (BC) or activated carbon (AC) with Fe3O4 nanoparticles, and their capacities to sorb methylene blue (MB) from water were evaluated and compared. Ball milling with magnetite not only improved the surface properties of the carbonaceous adsorbents, especially BC, but also introduced magnetic properties through mechanical extrusion. Furthermore, ball-mill extrusion increased the MB adsorption capacity of BC at all pH values by 14-fold, on average, but BC ball milled with magnetite had even greater MB adsorption capacity (27-fold, greater, on average). While ball milling of AC also improved its MB adsorption capacity (by almost 3-fold, on average), ball milling with magnetite did not further improve its MB adsorption capacity. All the magnetic adsorbents showed fast MB adsorption kinetics, reaching equilibrium within about 8 h. The Langmuir maximum MB adsorption capacity of the magnetic ball-milled BC (MBM-BC) was the highest (500.5 mg/g) among all the samples including the ones derived from AC. After five adsorption-desorption cycles, MBM-BC maintained about 80% MB removal capacity. The high MB adsorption capacity of MBM-BC was attributed to its increased surface area, opened pore structure, functional groups and aromatic CC bonds, which promoted π-π and electrostatic interactions. Findings from this study indicate that the magnetic ball-milled BC is a promising adsorbent due to its environmentally friendly synthesis, high efficiency, low cost, and convenience in operation.

Facile preparation of oxygen-rich activated carbon from petroleum coke for enhancing methylene blue adsorption

The oxygen-rich activated carbon (AC) was facilely developed using petroleum coke as a raw material by KOH activation under the rapid heating rate. The porosity and surface chemistry of ACs prepared under different heating rates were characterized and their adsorption properties for methylene blue (MB) were investigated. The results showed that the AC5 prepared under the heating rate of 5 °C min−1 had the highest surface area compared with the AC10, AC15 or AC20, while the AC20 prepared under the heating rate of 20 °C min−1 consisted of the highest oxygen content and most –OH functional group compares with the other ACs. These indicated that rapid heating rate was against the formation of more developed porosity, however, it was beneficial to producing more oxygen functional groups. As to MB adsorption, AC15 exhibited the maximum adsorption capacity for MB of 884 mg g−1 due to high surface area of 2803 m2 g−1 and high oxygen content of 23.27%. Moreover, despite the fact that AC20 had much lower surface area than the AC5, the AC20 showed higher MB adsorption capacity than the AC5. This was because the AC20 has the highest content of –OH, which was a positive impetus for MB adsorption. Therefore, rapid heating rate was an effective and simple approach to preparing the oxygen-rich ACs for improving the adsorption capacity of MB.

Magnetic BEA-type zeolites: preparation by dry-gel conversion method and assessment of dye removal performance

The large pores and the rather hydrophobic nature of silica-rich BEA-type zeolites make them promising dye adsorbents. Composites of such zeolites and magnetic particles (magnetic zeolites), commonly prepared using hydrothermal techniques, can be rapidly and reliably removed from treated wastewater through magnetic separation and are therefore more practical than conventional zeolites. However, the incorporation of magnetic particles is difficult to control since it depends greatly on whether the zeolite nucleation occurs in the vicinity of magnetic particles or not. To overcome this problem, we herein synthesize silica-rich magnetic BEA-type zeolites via a different route called dry-gel conversion, namely by exposing a precursor gel containing well-dispersed magnetite to water vapor at 180 °C for 12 h. The obtained samples were characterized by XRD and SEM–EDS and their dye adsorption performance were evaluated using methylene blue as a model. The results indicate that the precursor gel was successfully converted into BEA-type zeolites that contain homogeneously distributed magnetite, exhibit a high methylene blue adsorption capacity (133 mg/g), and can be easily separated by application of a magnetic field. Consequently, this study paves the way to the development of an efficient wastewater treatment technology and thus contributes to the establishment of a green society.

Novel Superadsorbent Highly Porous Hydrogel Based on Arabic Gum and Acrylamide Grafts for Fast and Efficient Methylene Blue Removal.

Environmental pollution with dyes released from industrial effluent is one of the major and most critical problems in the world. To alleviate this issue, advanced and safe materials with fast and highly efficient dye removal should be designed. Great attention has been paid recently to hydrogels based on polysaccharides such as Arabic Gum (AG) grafted with polyacrylamide (PAM) and polyacrylic acid (PAA). These materials combine the merits of natural polymers such as biodegradability and non-toxicity with the high adsorption ability of PAM and PAA towards cationic dyes such as methylene blue (MB). Many previous works have been done to enhance three-dimensional (3D) structure and swelling ability of the graft copolymers by using a crosslinking agent or even adding nanomaterials as a filler inside the hydrogel matrix. However, these additives may negatively affect the adsorption ability, and few previous studies could reach 2000 mg/g of maximum MB capacity removal within a good period of time. In our work, we synthesized partially hydrolyzed polyacrylamide grafted Arabic gum (AG-g-PAM/PAA) to have both amide and carboxylate groups. The modified water dissolved graft product undergoes water in oil (W/O) emulsion using paraffin oil as the continuous phase and Triton X-100 as a stabilizing agent; then, the system was inversed to oil in water (O/W) emulsion by increasing the shear mixing rate and cross-linked using Epichlorohydrin (ECH). The precipitated graft product showed hierarchically interconnected micro and macropores’ sponge like shape with fast water swelling and high MB adsorption capacity (2300 mg g−1) after 45 min at near neutral pH conditions.

Preparation of Salacca Peel Based Activated Carbon using CeCl3 Catalyzed Hydrothermal Carbonization and Microwave Induced KOH Chemical Activation as Ni-Ion Capacitor Electrode

Activated carbon is a highly porous non-graphite carbon material. Activated carbon has been used for various applications, namely adsorbent, catalyst support and electrode. As supercapacitor’s electrode, activated carbon has a high energy density and fast charge - discharge. In this study, salacca peel used as precursor to synthesized activated carbon through hydrothermal carbonization (HTC) and microwave induced chemical activation. The hydrochar (HC) was synthesized at 225°C, 5 bar for 5 h using cerium (III) chloride as catalyst. Furthermore, KOH was used as activating agent at various HC to KOH mass ratio at 1:2 (CE2), 1:3 (CE3), and 1:4 (CE4), under microwave irradiation at 700 W for 8 min. Activated carbon samples were analyzed using methylene blue adsorption capacity method, scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). The CE4 sample gave highest methylene blue adsorption capacity, indicating high surface area. This sample was used as nickel ion’s capacitor electrode with nickel oxide as the reference electrode and 6 M KOH as the electrolyte. The electrochemical characteristic was studied using cyclic voltammetry (CV) with various scan rates (2 mV/s, 5 mV/s, 10 mV/s) for the nickel ion’s capacitor electrode. It was obtained that CE4 provided higher capacitance compared to commercial activated carbon.

Biohybrid Hydrogel and Aerogel from Self-Assembled Nanocellulose and Nanochitin as a High-Efficiency Adsorbent for Water Purification.

A simple and novel method, self-assembly of nanocellulose and nanochitin, was developed to produce high-efficiency and versatile biohybrid hydrogel (BHH) and aerogel (BHA) for water purification. The self-assembly process was driven by the electrostatic force between one-dimensional (1D) negatively charged TEMPO-oxidized cellulose nanofiber (TOCNF) and positively charged partly deacetylated chitin nanofiber (PDChNF). The self-assembly process was performed at room temperature and without adding any cross-linking agents throughout the process. This results in the three-dimensional (3D) BHH that physically cross-linked via both electrostatic interactions and hydrogen bonding between TOCNF and PDChNF. The obtained BHA from lyophilized BHH exhibited a highly porous interconnected structure with a specific surface area of 54 m2·g-1, which assures the availability of its internal active site for the adsorption of toxic metalloid ions and organic pollutants. Consequently, the BHA displayed super-high adsorption capacities of 217 mg·g-1 for As(III) under the neutral pH conditions and 531 mg·g-1 for methylene blue (MB) under an alkaline aqueous condition with rapid adsorption kinetics, in sharp contrast to conventional biobased adsorbents. Moreover, the BHA is reusable, which still exhibited a high MB adsorption capacity of 505 mg·g-1 even after five successive adsorption-desorption cycles. This versatile BHA produced via a facile preparation strategy is proven to be a promising renewable adsorbent for water purification, offering simple and green alternatives to the conventional adsorbent from synthetic polymers.

Experimental Design Modeling of the Effect of Hexagonal Wurtzite-ZnO Synthesis Conditions on Its Characteristics and Performance as a Cationic and Anionic Adsorbent.

Surface composite design was used to study the effect of the ZnO synthesis conditions on its adsorption of methyl orange (MO) and methylene blue (MB). The ZnO was prepared via hydrothermal treatment under different conditions including temperature (T), precursor concentration (C), pH, and reaction time (t). Models were built using four Design expert-11 software-based responses: the point of zero charge (pHzc), MO and MB removal efficiencies (RMO, RMB), MO and MB adsorption capacities (qMO, qMB), and hydrodynamic diameter of ZnO particles (Dh). ZnO was characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, UV/VIS spectroscopy, thermal gravimetric analysis (TGA), and dynamic light scattering (DLS). The formation of ZnO was confirmed by the XRD, UV, and FTIR spectra. Results showed a very high efficiency for most of the samples for adsorption of MB, and more than 90% removal efficiency was achieved by 8 samples among 33 samples. For MO, more than 90% removal efficiency was achieved by 2 samples among 33 samples. Overall, 26 of 31 samples showed higher MB adsorption capacity than that of MO. RMB was found to depend only on the synthesis temperature while RMO depends on temperature, pH, and reaction time. pHzc was found to be affected by the synthesis pH only while Dh depends on the synthesis pH and precursor concentration.

Adsorption of selected dyes on Ti3C2Tx MXene and Al-based metal-organic framework

MXene and metal organic framework (MOF) were used as the main adsorbents to remove synthetic dyes from model wastewater. Methylene blue (MB) and acid blue 80 (AB) were used as the model cationic and anionic synthetic dyes, respectively. To investigate the physicochemical properties of the adsorbents used, we carried out several characterizations using microscopy, powder X-ray diffraction, a porosimetry, and a zeta potential analyzer. The surface area of MXene and MOF was 9 and 630 m2 g−1, respectively, and their respective isoelectric points were approximately pH 3 and 9. Thus, MXene and MOF exhibited high capacity for MB (~140 mg g−1) and AB (~200 mg g−1) adsorption, respectively due to their electrostatic attractions when the concentrations of the adsorbents and adsorbates were 25 and 10 mg L−1. Furthermore, the MOF was able to capture the MB due mainly to hydrophobic interactions. In terms of the advantages of each adsorbent according to our experimental results, MXene exhibited fast kinetics and high selectivity. Meanwhile, the MOF had a high adsorption capacity for both MB and AB. The adsorption mechanisms of both adsorbents for the removal of MB and AB were clearly explained by the results of our analyses of solution pH, ionic strength, and the presence of divalent cation, anion, or humic acids, as well as other characterizations (i.e., Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy). According to our results, MOF and MXene can be used as economical treatments for wastewater containing organic pollutants regardless of charge (e.g., MB and AB), and positively charged one (e.g., MB), respectively.

Eco-friendly complementary biosorption process of methylene blue using micro-sized dried biosorbents of two macro-algal species (Ulva fasciata and Sargassum dentifolium): Full factorial design, equilibrium, and kinetic studies

Finding green effective methods for dye removal from wastewater created an important interest in comparison to conventional methods. The aim of the present work was directed to study micro grinded dried biomass of two macro-algal species, Ulva fasciata and Sargassum dentifolium as complementary biosorbent materials for effective methylene blue (MB) removal from waste water. The two macro-algal species were collected, dried, and grinded by ball mill to get the micro size. After that, the biosorbent materials were characterized by FT-IR, TEM, and DLS. Furthermore, Full Factorial Design was applied to determine the optimum conditions that maximize the MB adsorption efficiency. Ulva fasciata biosorbent material was achieved the highest MB adsorption capacity, 97% of 328 mg/l MB with a maximum adsorption capacity (qmax) of 244 mg/g in comparison to the Sargassum dentifolium, 85.6% of 26 mg/l MB with (qmax) of 66.6 mg/g. Based on Factorial Design data the main effects of the Ulva biosorbent exhibited that both time & biosorbent dose had a positive effect on biosorption and both pH & MB concentrations have a negative effect, on the other hand, no temperature effect on both biosorbents. Point of zero charge (pHpzc) was recorded at pH 6.7 and 9 for Ulva and Sargassum biosorbents, respectively. The obtained results suggested that the two macro-algal species can be used in a complementary consecutive process where Ulva fasciata started first and followed by Sargassum dentifolium. The complementary treatment process achieved efficiency of 99.2% adsorption of 300 mg/l MB concentration. Moreover, the kinetic data suggested that the adsorption of MB follows the pseudo-second order model.